1. Field of the Invention
The present invention pertains to unilateral surface wave transducers that enable the transmission of a surface wave on the surface of a substrate in such a way that the essential part of the signal emerges by one end of this transducer and that the signal, if any, emerging by the other end has a very low level as compared with the main signal.
2. Description of the Prior Art
A known way of making single-phase unilateral transducers is to use internal reflectors, the reflection phase center of which is shifted with respect to that of the electroacoustic sources. For this purpose, generally, either floating electrodes or metal or dielectric layers superimposed on the metallizations of the electrodes are used. In the case of floating electrodes, their pitch or spacing is .lambda./8, and the etching precision needed to obtain this pitch therefore restricts the frequencies accessible. In the case of superimposed layers, a method of manufacture at several levels must be used, and this seriously complicates matters and substantially increases costs.